The invention relates to a magnetic device arranged at a curved section of the orbital path of electrically charged particles in an accelerator installation. The magnetic device is arranged around a beam guiding chamber surrounding the particle orbit and the device contains curved coil windings, which windings have convex outsides, concave insides and transition regions at the coil ends between these sides. The curved coil windings are built of superconducting rectangular conductors. A superconducting coil winding for a magnetic device of this nature is evident, for example, in the EP No. 190 623.
Accelerator installations for charged particles, for example electrons, frequently have storage rings, which, because of their curved particle orbits, must be provided with correspondingly curved dipole magnets. Such installations can, in particular, also be of the so-callad racetrack type. The racetrack particle orbit is composed of two semicircles with corresponding 180.degree. deflection magnets and of two straight orbit sections (cf. "Nucl. Instrum. and Meth.", Vol. 177, 1980, pages 411 to 416, or Vol. 204, 1982, pages 1 to 20). If the intent is to achieve high final energies, the magnetic fields of such deflection magnets can be generated, in particular, with superconducting coil windings.
The synchrotron radiation source known from DEP No. 35 30 446 also has an electron storage ring of the racetrack type. The synchroton radiation means the relative radiation emission of the electrons, which orbit at nearly the speed of light and, through deflection in a magnetic device, are kept in the proscribed particle orbit. Synchrotron radiation supplies x-ray radiation with parallel radiation characteristics and a high degree of intensity. This synchrotron radiation can advantageously be used for x-ray lithography which is especially suitable for the production of integrated circuits for generating microstructures.
In the production of the curved magnetic devices required for a storage ring, high demands are made with respect to the ability of their superconducting windings to maintain dimensions, in order to ensure the requisite field homogeneity. Appropriate windings can be built up, for example of superconducting rectangular conductors in accordance with methods evident in the above mentioned EP. Consistent with it, the conductors are wound around a central winding core with a convex outside and a concave inside as well as transition areas lying in between on a coil core and fixed. In this way, a planar winding results with the individual windings in this plane radially, with respect to the radius of curvature of the winding, arranged next to each other. In the magnetic device, the produced windings are so arranged that their winding planes come to lie at least largely parallel to the plane determined by the particle orbit.
In such radial construction of a curved superconducting coil winding however, the danger exists that when the superconductor is cooled to the operating temperature of for example 4.2 K., longitudinal changes can occur, which additionally, due to the curved winding form, differ markedly on the convex outside from those at the concave inside. Connected with this, especially at the coil ends, can be a displacement with respect to each other of the distinct conductors, which leads to undesirable field inhomogeneties.